Analytical procedures in the Rock Geochemical Laboratory of the Geological Survey of Denmark and Greenland

Kystol, Jørgen; Larsen, Lotte Melchior

doi:10.34194/ggub.v184.5230

Cited by 81 publications

(17 citation statements)

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“…After drying down the sample solutions, they were taken up with 1 ml concentrated HNO 3 and diluted further to 10 ml with ultrapure water. This solution was analyzed for trace elements using a Perkin Elmer ELAN 6000 DRS ICP-MS at the Geological Survey of Denmark and Greenland (GEUS), using international standards 43 . A comparison of GEUS’ analytical results on some standards with published values are contained in Kalsbeek and Frei 44 .…”

Section: Methodsmentioning

confidence: 99%

Oxidative elemental cycling under the low O2 Eoarchean atmosphere

Frei

Crowe

Bau

et al. 2016

Sci Rep

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The Great Oxidation Event signals the first large-scale oxygenation of the atmosphere roughly 2.4 Gyr ago. Geochemical signals diagnostic of oxidative weathering, however, extend as far back as 3.3–2.9 Gyr ago. 3.8–3.7 Gyr old rocks from Isua, Greenland stand as a deep time outpost, recording information on Earth’s earliest surface chemistry and the low oxygen primordial biosphere. Here we find fractionated Cr isotopes, relative to the igneous silicate Earth reservoir, in metamorphosed banded iron formations (BIFs) from Isua that indicate oxidative Cr cycling 3.8–3.7 Gyr ago. Elevated U/Th ratios in these BIFs relative to the contemporary crust, also signal oxidative mobilization of U. We suggest that reactive oxygen species were present in the Eoarchean surface environment, under a very low oxygen atmosphere, inducing oxidative elemental cycling during the deposition of the Isua BIFs and possibly supporting early aerobic biology.

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Section: Methodsmentioning

confidence: 99%

Oxidative elemental cycling under the low O2 Eoarchean atmosphere

Frei

Crowe

Bau

et al. 2016

Sci Rep

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“…Porphyritic textures observed among the sections represent polygenetic of these basaltic rocks that probably involves a multi-stage cooling history for the melt. The presence of a variety of plagioclase shapes and sizes may indicate different stages in the cooling history but rather more likely to be affected by the sudden changes in the degree of super cooling (∆T) or in the number of nuclei [24].…”

Section: Petrography Of Basaltic Rocksmentioning

confidence: 99%

Characterization and Origin of the Miocene Mudawwara-Quwayra Basaltic Dike, Southern Jordan

Alnawafleh¹,

Tarawneh²,

Ibrahim³

et al. 2015

IJG

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Petrographic, mineralogical and geochemical investigations were carried out on representative samples from the Mudawwara-Quwayra Dike (MQD) in southern Jordan. The MQD intruded Paleozoic and Cretaceous rocks as sub-vertical basaltic plugs, striking NW-SE along a fault zone and extending for more than 100 km. The MQD forms irregularly positive features, and is represented by symmetrical, elliptical, elongated or circular hills. It comprises thin basaltic layers intercalated with pyroclastics and inclusions of different size and lithology, including limestone, sandstone, phosphate, quartzite, and marble. Petrographically, the rock exhibits phyric, porphyritic, vitrophyric and locally glomerophyritic textures manifested by plagioclase, clinopyroxene and rare olivine and set in a matrix of plagioclase, pyroxene, brown glass and opaque phases. Clinopyroxene and olivine phenocyrsts show disequilibrium textures such as reaction/resorbed rims in the forms of corroded ends. The paragenetic sequence shows that olivine is the first phase to be crystallized and coexisting with pyroxene at sometime, while pyroxene continues crystallization. Plagioclase might have crystallized in contemporaneous later than the pyroxene. The MQD rocks are classified as basalt and exhibit a narrow range of silica with a unique subalkaline affinity. This is most probably attributed to assimilation of the abundant siliciclastic inclusions by the ascending magma. Emplacement of the MQD is attributed to regional phase of magmatism in Jordan and Saudi Arabia, which is probably the peripheral extension of a large magmatic event widely exposed in the Red Sea realm.

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“…The data are presented in Table 1 in the online supplementary material. See Kystol and Larsen (1999) for a detailed description of the analytical procedures.…”

Section: Whole Rock Major and Trace Element Analysismentioning

confidence: 99%

Mesoarchaean aluminous rocks at Storø, southern West Greenland: New age data and evidence of premetamorphic seafloor weathering of basalts

Szilas

Garde

2013

Chemical Geology

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Metamorphosed Meso-to Neoarchaean supracrustal rocks in the central part of the island of Storø (Nuuk region, southern West Greenland), show field-and geochemical evidence of premetamorphic chemical alteration. This alteration changed basaltic precursors into aluminous lithologies, and following amphibolite grade metamorphism and penetrative ductile deformation, these garnet-biotite schists now resemble adjacent metapelitic schists of sedimentary origin. Mass balance calculations (isocon method), suggests that most major elements (Si, Fe, Mg, Ca, Na and P) were leached during alteration. The calculated overall net mass changes are between-18% and-45%, consistent with breakdown of olivine, pyroxenes, plagioclase and apatite in the basaltic precursor rocks. Major and trace elements such as, K, Cs, Rb, Ba, Pb, Zn, La, Ce were added during this alteration process, whereas high field strength elements (Ti, Al, Zr, Hf and Nb) remained essentially immobile and were thus residually enriched. Interestingly, Th which is generally assumed to be immobile in fluids, was also added during this process. These chemical changes reflect interaction between a basaltic protolith and hydrous fluids that established a new equilibrium and thus a different mineral assemblage. It is proposed that the premetamorphic alteration at Storø was due to low-temperature interaction between seawater and oceanic crust, and thus essentially represents in situ submarine seafloor weathering. This interpretation is consistent with the mass balances reported from welldocumented examples in younger settings. New U-Pb zircon geochronology from the arc-related mafic sequences at Storø shows that they comprise at least two distinct age groups: an older anorthosite complex dated at 3051.3 ± 2.6 Ma and a younger supracrustal sequence with age brackets between 2840-2710 Ma. The allochthonous nature of these two mafic igneous to sedimentary stacks is consistent with accretionary processes in island arc complexes and a compressional Archaean tectonic setting.

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Analytical procedures in the Rock Geochemical Laboratory of the Geological Survey of Denmark and Greenland

Cited by 81 publications

References 0 publications

Oxidative elemental cycling under the low O2 Eoarchean atmosphere

Oxidative elemental cycling under the low O2 Eoarchean atmosphere

Characterization and Origin of the Miocene Mudawwara-Quwayra Basaltic Dike, Southern Jordan

Mesoarchaean aluminous rocks at Storø, southern West Greenland: New age data and evidence of premetamorphic seafloor weathering of basalts

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